Self-Powered Nuclear Detector Bias Voltage
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Solution Overview
Problem
Existing self-powered neutron detectors in nuclear reactors have reduced sensitivity due to electrical potential troughs in the insulating annulus, which prevents low-energy electrons and photoelectrons from contributing to the detector current, necessitating long, expensive signal cables and complex signal processing to compensate for variable sensitivity across the reactor core.
Innovation Solution
Applying a negative bias voltage of approximately 1 to 30 volts, preferably between 1 and 2 volts, to the neutron sensitive emitter element, along with a selenium coating on the emitter, to enhance the detection of gamma-induced and beta-induced signals, thereby increasing the detector's sensitivity and allowing more electrons to be counted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a negative bias voltage is applied to the emitter element, then the detector sensitivity is improved by overcoming the insulator's potential trough, but the device complexity increases due to the additional voltage application mechanism
Solution Approach 1:
The emitter element serves dual functions: it detects neutrons and simultaneously serves as the electrode for applying the negative bias voltage. The insulator that normally just provides electrical isolation is repurposed to also apply the bias voltage to the emitter. This self-service approach improves sensitivity without requiring separate voltage application mechanisms, thus limiting the increase in device complexity.
2Reliability
If the insulator thickness is increased to improve electrical isolation, then the reliability of electrical isolation is improved, but the detector sensitivity deteriorates due to increased potential trough depth preventing low-energy electron detection
Solution Approach 1:
The patent changes the electrical parameter of the insulator by applying a negative bias voltage to the emitter, which fundamentally alters the potential distribution within the insulator. This parameter change allows the system to overcome the potential trough problem without requiring changes to the insulator's physical dimensions, thus maintaining both reliable electrical isolation and improved detector sensitivity.
3Reliability
If long signal cables are used to transmit signals from the detector, then the reliability of signal transmission in hostile environments is improved, but the cost and signal-to-noise ratio deteriorate
Solution Approach 1:
The negative bias voltage is applied preliminarily to the emitter to overcome the potential trough before electrons reach the insulator. This preliminary action ensures that electrons with sufficient energy can penetrate the insulator and reach the collector, thereby improving the signal strength before transmission. This reduces the need for long cable runs and improves the signal-to-noise ratio while maintaining reliable signal transmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The negative bias voltage improves the sensitivity of self-powered neutron detectors by overcoming the insulator's potential trough, enabling the detection of previously undetected electrons and photoelectrons, which simplifies signal interpretation and reduces the need for long signal cables, leading to more accurate and consistent power distribution measurements within the reactor core.
Implementation Method 1
A neutron sensitive material, such as vanadium, is employed for the emitter element 12 and emits electrons in response to neutron irradiation
Implementation Method 2
Applying a negative bias voltage of approximately 1 to 30 volts, preferably between 1 and 2 volts, to the neutron sensitive emitter element, along with a selenium coating on the emitter, to enhance the detection of gamma-induced and beta-induced signals
Implementation Method 3
a selenium coating on the emitter, to enhance the detection of gamma-induced and beta-induced signals
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A self-powered neutron detector having an emitter with a slightly negative bias voltage that assures that an increase in the electrons that enter the insulator are counted and decreases or eliminates the gamma induced prompt signal. Variations in the size of the bias is used as a diagnostic tool to estimate the gamma induced prompt signal.